CN104062484A - Method for testing body leakage current and surface leakage current of HEMT device - Google Patents

Abstract

The invention discloses a method for testing body leakage current and surface leakage current of an HEMT device. The method mainly solves the problem that separated testing of the body leakage current and the surface leakage current can not be carried out on gate leakage current of a conventional HEMT device in the prior art. According to the realizing scheme, two testing auxiliary devices with the same structure as the tested HEMT device are manufactured, wherein the gate electrode sizes of the testing auxiliary devices are different; semi-conductor parameter testing equipment is utilized for testing the gate leakage current of the tested HEMT device and the gate leakage current of the two testing auxiliary devices respectively; the body leakage current of the tested HEMT device is obtained by subtracting the gate leakage current of one testing auxiliary device from the gate leakage current of the other testing auxiliary device; the surface leakage current of the tested HEMT device is obtained by subtracting the gate leakage current of the tested HEMT device from the body leakage current of the tested HEMT device. The testing method is fast and easy to carry out, the result is accurate and reliable, and the basis is provided for analyzing the production mechanism of the body leakage current and the surface leakage current in the follow-up stage, and improving the reliability of the HEMT device.

Description

The method of test HEMT device body leakage current and surface leakage current

Technical field

The invention belongs to microelectronics technology, the particularly discrete testing method of high electron mobility heterojunction transistor HEMT device grid leakage current, for improving the reliability of HEMT device.

Background technology

Third generation broad stopband gap semiconductor taking GaN as representative has with it that energy gap is large, breakdown electric field is high, the more high characteristic of thermal conductivity in recent years, is subject to extensive concern.There is the two-dimensional electron gas of high concentration, high mobility in the high electron mobility heterojunction transistor HEMT that particularly material such as GaN and AlGaN forms, utilizes HEMT device prepared by these characteristics to have huge advantage and application prospect at aspects such as making high frequency, high pressure and high power electronic device and microwave device at heterojunction boundary place.Therefore GaN HEMT is the study hotspot of Chinese scholars always in recent years, and has obtained a large amount of significant achievements in research.

Along with the development of GaN HEMT, its grid leakage current is increasing on the impact of device performance and reliability.Conventionally, HEMT device selects metal as grid material, and the Schottky gate that this metal/semiconductor forms tends to form obvious grid leakage current.These extra grid leakage currents can increase low-frequency noise and the quiescent dissipation of device, inducing current avalanche phenomenon, reduce device efficiency and reduce the voltage breakdown of HEMT device and then reduce output power etc.Therefore, grid leakage current becomes one of important research direction of HEMT device reliability gradually.

HEMT device grid leakage current mainly comprises three parts: body leakage current, surface leakage current and table top leakage current.At present, mesa edge leakage current can be realized preferably and being controlled by special process, thereby first two leakage current is occupied an leading position in grid leakage current.Body leakage current is not identical with the formation mechanism of surface leakage current, produces rule and model in order more profoundly to study it, just must carry out Quantitative Separation to this two parts electric current.But so far, do not find simple and effective current separation method, only depending on conventional method of testing is to be not enough to grid leakage current to carry out accurate study.2006, the people such as W.S.Tan proposed the HEMT device Schottky gate current separation structure based on double grid, and this structure is carried out release surface leakage current by increase an electrode between grid and drain electrode.But this structure also makes it and conventional H EMT device distinguish to some extent, and manufacture craft is comparatively complicated, has larger limitation for further research HEMT device at the performance degradation under actual working state.

Along with constantly dwindling of HEMT device feature size, the impact that Schottky gate leakage current brings aspects such as associated materials growth and device technology optimization, the research of component failure mechanism and Performance Evaluations is increasing, therefore the body leakage current and the surface leakage current that are sought after isolating in grid leakage current carry out Analysis on Mechanism, and then improve the reliability of device.

Summary of the invention

The object of the invention is to propose a kind of method of the HEMT of test device body leakage current and surface leakage current, with the Quantitative Separation problem of body leakage current and surface leakage current in solution Schottky gate leakage current, for Material growth and the device technology optimization of HEMT device, and defect characterizes, reliability assessment provides guidance.

For achieving the above object, technical scheme of the present invention comprises the steps:

A. make test additional device:

(A1) making structure is identical with tested HEMT device architecture, and the different HEMT first of electrode parameter tests additional device; This first test additional device, its gate electrode length is L _g'=L _g+ 2 Δ L, width is W _g'=W _g+ 2 Δ L, gate electrode and source electrode distance are L _gs'=L _gs-Δ L, the distance of grid and drain electrode is L _gd'=L _gd-Δ L, wherein Δ L is grid size increment, L _gs> Δ L>0, L _g, W _gbe respectively grid length and the grid width of tested HEMT device, L _gsfor grid and the source electrode distance of tested HEMT device, L _gdfor the grid and drain electrode distance of tested HEMT device;

(A2) in testing the gate electrode of additional device, removes HEMT first metallic region onesize with tested HEMT device gate electrode, formation gate electrode is that the HEMT second of rectangle frame structure tests additional device, in this each limit of rectangle frame housing and its, be Δ L, L without the distance on each limit, metal deposit rectangular area _gs> Δ L>0, the i.e. outer frame length of gate electrode rectangle frame and width L respectively _g+ 2 Δ L, W _g+ 2 Δ L;

B. utilize semiconductor parametric test equipment to test out respectively following three curves:

Tested HEMT device is placed in to closed condition, applies continually varying bias voltage V in drain electrode, measure the grid leakage current I of tested HEMT device _{g (V)}relation curve P3 with bias voltage V;

By the test condition identical with tested HEMT device, measure HEMT first and test the grid leakage current of additional device relation curve P1 with bias voltage V;

By the test condition identical with tested HEMT device, measure HEMT second and test the grid leakage current of additional device relation curve P2 with bias voltage V;

C. according to three curve P1 measured in step B, P2 and P3, obtain the body leakage current I of tested HEMT device _{b (V)}with surface leakage current I _{s (V)}:

(C1) test the grid leakage current grid leakage current corresponding with each bias voltage V in drain bias relation curve P1 of additional device with described HEMT first with the grid leakage current under bias voltage V corresponding in described relation curve P2 poor one by one, obtain the body leakage current I of tested HEMT device _{b (V)}with bias voltage V relation curve P4;

(C2) with the grid leakage current of the tested HEMT device grid leakage current I corresponding with each bias voltage V in bias voltage relation curve P3 _{g (V)}deduct one by one the body leakage current of tested HEMT device and body leakage current I under corresponding bias voltage V in drain bias relation curve P4 _{b (V)}, obtain the surface leakage current I of tested HEMT device _{s (V)}with bias voltage V relation curve P5;

(C3) described two relation curve P4 and P5 are plotted in the same coordinate system, obtain within the scope of bias voltage surface leakage current I in the grid leakage current of the tested HEMT device under drain voltage arbitrarily _{s (V)}with body leakage current I _{b (V)}.

The present invention compared with prior art tool has the following advantages:

1) used test device of the present invention is all manufactured as basis taking conventional three end HEMT device technologies, does not change device architecture, only changes device gate electrode area and size, and technology is stable, and manufacture difficulty and cost are all low than prior art;

2) while test, only need, by semiconductor parametric test equipment, the different HEMT devices of three grid areas are carried out respectively to an electrical measurement, surveyed grid leakage current, by simple numerical evaluation, can be obtained to tested HEMT device grid leakage current I _{g (V)}middle body leakage current I _{b (V)}with surface leakage current I _{s (V)}size, realize grid leakage current Quantitative Separation test;

3) method of testing of the present invention is quick, easy than existing methods; Separating resulting accurately, reliably, its body leakage current of measuring is conducive to the material relevant to HEMT device to surface leakage current and structure is carried out process optimization and assessment, for the body leakage current in subsequent analysis grid leakage current and surface leakage current mechanism of production provide foundation, and then provide new solution for the reliability that improves HEMT device.

Brief description of the drawings

Fig. 1 is realization flow figure of the present invention;

Fig. 2 is tested HEMT device architecture and grid leakage current composition schematic diagram;

Fig. 3 is tested HEMT device electrode structural representation in the present invention;

Fig. 4 is that in the present invention, HEMT first tests additional device electrode structure schematic diagram;

Fig. 5 is that in the present invention, HEMT second tests additional device electrode structure schematic diagram;

Fig. 6 is the circuit theory diagrams of testing HEMT device grid leakage current in the present invention;

Fig. 7 is that the present invention utilizes Fig. 6 to test out the HEMT device grid leakage current graph of three different electrode structure;

Fig. 8 is body leakage current and the surface leakage current figure of the tested HEMT device measured with the present invention.

Embodiment

Below in conjunction with drawings and Examples, the specific embodiment of the present invention is described in further detail.Following examples are used for illustrating the present invention, but are not used for limiting the scope of the invention.

Below in conjunction with accompanying drawing, test philosophy of the present invention and method of testing are expressed in further detail.

One. test philosophy

Three HEMT devices related in this example are through the processing of table top special process, in grid leakage current, table top leakage current all can be ignored, for tested HEMT device 3, its grid leakage current comprises two parts: the lateral surfaces leakage current I between Schottky gate and source-drain electrode _{s (V)}, the body leakage current I forming by barrier layer perpendicular to Schottky gate surface _{b (V)}, as shown in Figure 2, two electric currents are all functions of drain bias voltage V, wherein, and surface leakage current I _{s (V)}size and grid divide the distance between the source of being clipped to, drain electrode inversely proportional relation, body leakage current I _{b (V)}size and gate electrode area relation in direct ratio.

For tested HEMT device 3, if utilize semiconductor parametric tester to apply fixed bias voltage V0 at the element leakage utmost point, can only record its total grid leakage current I _{g (V0)}, can not record surface leakage current I in its gate current _{s (V0)}with body leakage current I _{b (V0)}.The features of mating surface leakage current of the present invention and body leakage current, on tested HEMT device architecture basis, design two HEMT test additional devices that gate electrode area is different, and the gate electrode size differing is identical with tested HEMT device grid area, be under fixed numbers condition at drain electrode bias voltage, the body leakage current I of the difference of the body leakage current of two additional devices and tested HEMT device _{b (V0)}numerical value identical, the gate electrode of two test additional devices is all identical with the distance of its source, drain electrode respectively simultaneously, identical to ensure the surface leakage current of two test additional devices, be fixed as grid leakage current under V0 condition with two HEMT test additional devices at bias voltage poor, its result is the body leakage current I of tested HEMT device _{b (V0)}.Recycle tested HEMT device grid leakage current I _{g (V0)}body leakage current I with gained _{b (V0)}make the surface leakage current I that difference can further obtain tested HEMT device _{s (V0)}, realize tested HEMT device 3 body leakage current I in gate current under fixed bias voltage V0 condition _{b (V0)}with surface leakage current I _{s (V0)}discrete testing.

When the present embodiment test, by be biased continually varying voltage V at drain electrode, record the grid leakage current of tested HEMT device under each bias voltage and two HEMT test additional devices, thereby obtain the relation curve of tested HEMT device grid leakage current and bias voltage, HEMT first tests the relation curve of additional device grid leakage current and bias voltage and HEMT second and tests the relation curve of additional device grid leakage current and bias voltage.In order to realize the surface leakage current I of tested HEMT device _{s (V)}with body leakage current I _{b (V)}discrete testing, only need utilize successively above-mentioned separation principle to calculate grid leakage current corresponding to each bias voltage V in three described relation curves, can obtain surface leakage current and the body leakage current of the tested HEMT device under each bias voltage, thereby obtain the surface leakage current I of tested HEMT device _{s (V)}relation curve and body leakage current I with drain electrode bias voltage V _{b (V)}with the relation curve of drain electrode bias voltage V, the body leakage current I that can setover in scope under bias voltage V arbitrarily according to above-mentioned two curves _{b (V)}with surface leakage current I _{s (V)}.

Two. method of testing

With reference to Fig. 1, the testing procedure that the present invention carries out HEMT device body leakage current and surface leakage current according to above-mentioned principle is as follows:

Steps A, makes two HEMT test additional devices.

Two HEMT test additional devices are all taking tested HEMT device 3 structures as basis, and wherein as shown in Figure 2, it is followed successively by substrate layer to tested HEMT device 3 structures from top to bottom, intrinsic gallium nitride layer and aluminum gallium nitride barrier layer; Aluminum gallium nitride barrier layer is provided with electrode.As shown in Figure 3, it is from left to right followed successively by source electrode to the structural relation of electrode, conductivity gate and drain electrode, and wherein source electrode and drain electrode is measure-alike, and length is L _t=10 μ m, width is W _t=200 μ m; The grid length of conductivity gate is L _g=1 μ m, grid width is W _g=200 μ m, the distance between grid and source electrode is L _gs=3um, the distance between grid and drain electrode is L _gd=3 μ m.

(A1) manufacture HEMT first and test additional device 1:

Change the gate electrode size of tested HEMT device 3, expand gate electrode size, dwindle the distance of gate electrode and source electrode, gate electrode and drain electrode, make the first test additional device 1 that structure is identical with tested HEMT device architecture, this the first test additional device 1 is than tested HEMT device 3, the each Δ L that increases by 2 times of the length of its gate electrode and width, gate electrode and source-drain electrode distance are respectively dwindled Δ L.As shown in Figure 4, design parameter is as follows:

The long L of grid _g'=L _g+ 2 Δ L, grid width W _g'=W _g+ 2 Δ L, gate electrode and source electrode distance L _gs'=L _gs-Δ L, the distance L of gate electrode and drain electrode _gd'=L _gd-Δ L, wherein 3 μ m> Δ L>0, get Δ L=1 μ m in this example;

(A2) manufacture HEMT second and test additional device 2:

In HEMT first tests the gate electrode of additional device 1, remove the metallic region onesize with tested HEMT device gate electrode, the HEMT second that forms gate electrode and be rectangle frame structure tests additional device 2, as shown in Figure 5.In this each limit of rectangle frame housing and its, be Δ L without the distance on each limit, metal deposit rectangular area, 3 μ m> Δ L>0, get in this example Δ L=1 μ m, the outer frame length of gate electrode rectangle frame and width are tested the long L of additional device grid with HEMT first respectively _g' and grid width W _g' identical.

Step B, tests respectively the grid leakage current of tested HEMT device and two HEMT test additional devices.

Test in this step is to utilize semiconductor testing apparatus to carry out, and test circuit as shown in Figure 6, by the source ground of device, utilizes semiconductor testing apparatus to apply voltage V at grid _gmake device in closed condition, apply continuous bias voltage V in drain electrode, testing apparatus can record gate current I _{g (V)}corresponding relation curve with bias voltage V.

(B1) apply continuously the bias voltage V of 0V to 20V in the drain electrode of tested HEMT device, record the grid leakage current I of tested HEMT device _{g (V)}relation curve P3 with bias voltage V;

(B2) drain electrode of testing additional device at HEMT first applies the bias voltage V of 0V to 20V continuously, records HEMT first and test the grid leakage current of additional device relation curve P1 with bias voltage V;

(B3) drain electrode of testing additional device at HEMT second applies the bias voltage V of 0V to 20V continuously, records HEMT second and test the grid leakage current of additional device relation curve P2 with bias voltage V;

(B4) by above-mentioned three Drawing of Curves in the same coordinate system, as shown in Figure 7, its ordinate is the absolute value of grid leakage current, horizontal ordinate is the voltage bias between drain electrode and source electrode, numerical value is for just.

As seen from Figure 7, the variation tendency of three curves is basic identical, just in the order of magnitude of gate current, has any different.Can obtain the tested HEMT device under any bias voltage and two grid leakage current data that HEMT tests additional devices within the scope of 0 to 20V by Fig. 7.

Step C, according to the test result in step B, calculates tested HEMT device surface leakage current and body leakage current.

(C1) define the grid leakage current expression of tested HEMT device and two HEMT test additional devices:

Comprise that according to the grid leakage current of HEMT device the two-part principle of surface leakage current body leakage current obtains the grid leakage current expression of described three HEMT devices:

For the grid leakage current of tested HEMT device 3 and the relation curve P3 of bias voltage, the gate leakage current I that its each bias voltage V is corresponding _{g (V)}include body leakage current I _{b (V)}and surface leakage current I _{s (V)}two parts, its expression is:

I _g(V)＝I _b(V)+I _s(V)； <1>

Test the grid leakage current of additional device 1 and the relation curve P1 of bias voltage for HEMT first, gate leakage current corresponding to its each bias voltage V include body leakage current and surface leakage current two parts, its expression is:

${\hat{I}}_{g\left(V\right)}={\hat{I}}_{s\left(V\right)}+{\hat{I}}_{b\left(V\right)};---<2>$

Test the grid leakage current of additional device 2 and the relation curve P2 of bias voltage for HEMT second, gate leakage current corresponding to its each bias voltage V include body leakage current and surface leakage current two parts, its expression is:

${\stackrel{\&CenterDot;\&CenterDot;}{I}}_{g\left(V\right)}={\stackrel{\&CenterDot;\&CenterDot;}{I}}_{s\left(V\right)}+{\stackrel{\&CenterDot;\&CenterDot;}{I}}_{b\left(V\right)};---<3>$

(C2) calculate the body leakage current I of tested HEMT device 3 _{b (V)}:

Because testing distance between grid that distance and HEMT second between the grid of additional device 1 and source-drain electrode test additional device 2 and source-drain electrode, HEMT first all equates, thereby HEMT first tests the grid leakage current of additional device and the relation curve P1 of bias voltage and HEMT second and tests the surface leakage current in the grid leakage current under each bias voltage V in the grid leakage current of additional device and the relation curve P2 of bias voltage and all equate, simultaneous formula <2> and <3> also bring above formula to obtain into:

${\hat{I}}_{b\left(V\right)}-{\stackrel{\&CenterDot;\&CenterDot;}{I}}_{b\left(V\right)}={\hat{I}}_{g\left(V\right)}-{\stackrel{\&CenterDot;\&CenterDot;}{I}}_{g\left(V\right)};---<4>$

Identical with the grid area of tested HEMT device 3 according to the difference of grid area of two HEMT test additional devices, can obtain HEMT first and test the grid leakage current of additional device and be equal to the body leakage current I under corresponding bias voltage V in described relation curve P3 with the difference of body leakage current in grid leakage current under each bias voltage V in bias voltage relation curve P1 and described relation curve P2 _{b (V)}, and then formula <4> is expressed as:

$I_{b\left(V\right)}={\hat{I}}_{g\left(V\right)}-{\stackrel{\&CenterDot;\&CenterDot;}{I}}_{g\left(V\right)};---<5>$

According to formula <5>, test the grid leakage current grid leakage current corresponding with each bias voltage V in bias voltage relation curve P1 of additional device with HEMT first with the grid leakage current under corresponding bias voltage V in described relation curve P2 poor one by one, can obtain the body leakage current I of tested HEMT device 3 _{b (V)}with bias voltage V relation curve P4.

(C3) calculate the surface leakage current I of tested HEMT device 3 _{s (V)}:

According to expression formula <1>, the surface leakage current I in the grid leakage current of tested HEMT device 3 and bias voltage relation curve P3 in the grid leakage current of each point _{s (V)}can be expressed as:

I _s(V)＝I _g(V)-I _b(V)； <6>

According to formula <6>, with the grid leakage current of the tested HEMT device 3 grid leakage current I corresponding with each bias voltage V in bias voltage relation curve P3 _{g (V)}deduct one by one the body leakage current of tested HEMT device 3 and body leakage current I under corresponding bias voltage V in bias voltage relation curve P4 _{b (V)}, obtain the surface leakage current I of tested HEMT device 3 _{s (V)}with bias voltage V relation curve P5.

(C4) by the body leakage current I of tested HEMT device 3 _{b (V)}with the relation curve P4 of bias voltage V and the surface leakage current I of tested HEMT device 3 _{s (V)}be plotted in the same coordinate system with the relation curve P5 of bias voltage V, as shown in Figure 8, in figure, ordinate is the absolute value of grid leakage current, and horizontal ordinate is the voltage bias of drain electrode, and numerical value is for just.

Can be obtained within the scope of 0 to 20V surface leakage current I in the grid leakage current of the tested HEMT device 3 under bias voltage arbitrarily by Fig. 8 _{s (V)}with body leakage current I _{b (V)}data.

The foregoing is only preferred embodiment of the present invention; not in order to limit the present invention; obviously for those skilled in the art; understanding after content of the present invention and principle; any amendment of doing within the spirit and principles in the present invention, be equal to and replace and improvement etc., within all should being included in protection scope of the present invention.

Claims (1)

1. a method of testing HEMT device body leakage current and surface leakage current, comprises the steps:

A. make test additional device:

(A1) making structure is identical with tested HEMT device (3) structure, and the different HEMT first of electrode parameter tests additional device (1); This first test additional device, its gate electrode length is L _g'=L _g+ 2 Δ L, width is W _g'=W _g+ 2 Δ L, gate electrode and source electrode distance are L _gs'=L _gs-Δ L, the distance of grid and drain electrode is L _gd'=L _gd-Δ L, wherein Δ L is grid size increment, L _gs> Δ L>0, L _g, W _gbe respectively grid length and the grid width of tested HEMT device (3), L _gsfor grid and the source electrode distance of tested HEMT device (3), L _gdfor the grid and drain electrode distance of tested HEMT device (3);

(A2) in testing the gate electrode of additional device (1), removes HEMT first metallic region onesize with tested HEMT device gate electrode, formation gate electrode is that the HEMT second of rectangle frame structure tests additional device (2), in this each limit of rectangle frame housing and its, be Δ L, L without the distance on each limit, metal deposit rectangular area _gs> Δ L>0, the i.e. outer frame length of gate electrode rectangle frame and width L respectively _g+ 2 Δ L, W _g+ 2 Δ L;

B. utilize semiconductor parametric test equipment to test out respectively following three curves:

Tested HEMT device is placed in to closed condition, applies continually varying bias voltage V in drain electrode, measure the grid leakage current I of tested HEMT device _{g (V)}relation curve P3 with bias voltage V;

By the test condition identical with tested HEMT device, measure HEMT first and test the grid leakage current of additional device relation curve P1 with bias voltage V;

By the test condition identical with tested HEMT device, measure HEMT second and test the grid leakage current of additional device relation curve P2 with bias voltage V;

C. according to three curve P1 measured in step B, P2 and P3, obtain the body leakage current I of tested HEMT device _{b (V)}with surface leakage current I _{s (V)}:

(C1) test the grid leakage current grid leakage current corresponding with each bias voltage V in drain bias relation curve P1 of additional device with described HEMT first with the grid leakage current under bias voltage V corresponding in described relation curve P2 poor one by one, obtain the body leakage current I of tested HEMT device _{b (V)}with bias voltage V relation curve P4;

(C2) with the grid leakage current of the tested HEMT device grid leakage current I corresponding with each bias voltage V in bias voltage relation curve P3 _{g (V)}deduct one by one the body leakage current of tested HEMT device and body leakage current I under corresponding bias voltage V in drain bias relation curve P4 _{b (V)}, obtain the surface leakage current I of tested HEMT device _{s (V)}with bias voltage V relation curve P5;

(C3) described two relation curve P4 and P5 are plotted in the same coordinate system, obtain within the scope of bias voltage surface leakage current I in the grid leakage current of the tested HEMT device under drain voltage arbitrarily _{s (V)}with body leakage current I _{b (V)}.